Feedback Carburetor System: Description

The Electronic Control Unit (ECU) uses sensor input signals in conjunction with vacuum and fuel regulating solenoids to maintain proper air/fuel ratio during most engine operating conditions. The ECU also controls an idle boost system which compensates for engine loads on vehicles equipped with automatic transmission and/or air conditioning. Vehicle is also equipped with a fuel cut-off system.

The feedback fuel system consists of 4 subsystems: "X", "M", idle feedback and fuel cut-off. The "X" subsystem consists of air control valve B, feedback control solenoid valve, frequency solenoid valve B, Constant Vacuum (CV) generator, check valve, pulse rectifier and silencer.

The "M" subsystem consists of air control valve A and frequency solenoid valve A. Frequency solenoid valve C is used only on vehicles equipped with automatic transmission.

The idle feedback subsystem consists of air bleed valve B and the air leak solenoid valve. To reduce idle emissions, both the air bleed valve B and the air leak solenoid valve operate when the air injection to the exhaust manifold is cut off.

The fuel cut-off subsystem consists of an ECU controlled primary slow mixture cut-off solenoid valve in the carburetor. Solenoid cuts off idle fuel mixture when ignition is turned off or vehicle is under deceleration.